John C. Martin's design patents Des. 365,600, issued Dec. 26, 1995, Des. 390,698, issued Feb. 17, 1998, and Des. 394, 153, issued May 12, 1998, disclose an ornamental design for an oil change reminder for key rings. U.S. Pat. No. 5,705,977, issued Jan. 6, 1998, to James Jones, discloses a memory device which includes a programmable processor to signal a user when a recommended service interval has elapsed.